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Topic Review (Newest First)

10-14-2012 07:36 PM

cobalt327

Who said they were "the same"? I did say

Quote:

Your 148 heads are more like the c/n 215 heads as far as the chamber volume goes.

. As in smaller chamber, not the bigger chamber seen on the 049/781, etc. heads.

10-14-2012 06:12 PM

OMARS67

Thanks fellas very informative.That's exactly what I need to know. I think I'll invest some $$$ into the 049 heads.

10-14-2012 11:14 AM

cobalt327

Quote:

Originally Posted by OMARS67

so is it safe to say that if the 049 and my 148 were cc close and both had 2.19 vavles they would produce close to the same power. thank for the response guys.

Your 148 heads are more like the c/n 215 heads as far as the chamber volume goes. They're sometimes called "semi-open" chambers and should be about 110-112cc.

If the CR was the same there wouldn't be much difference in performance between the two heads. Getting compression is easier w/the smaller chambers especially if building a small BBC (396/402). In a 454 engine, watch that the compression isn't too high.

Fitting larger exhaust valves in the semi open chamber requires some finesse to minimize shrouding.

come on man.. is that response needed??? you answer my question by saying my 148 may have a different runner. just that would have been fine. cobalt327 answer by agreeing my compression would go up after saying theres different variable effecting compression . then i ask if the difference between my 148 and the 049 is the runner volume/design assuming the valve size is the same and the cc volume and all other variables between the two heads. that shouldnt be a broad assumption.

10-13-2012 11:57 AM

OMARS67

so is it safe to say that if the 049 and my 148 were cc close and both had 2.19 vavles they would produce close to the same power. thank for the response guys.

10-13-2012 09:28 AM

OMARS67

yeah i figured it wouldnt be worth the time. the reason i ask is because i have a set of 049 heads. and i read there the best hi perf head for oval BBC. what so special?? 049 have advertise smaller cc chamber. maybe the intake runner volume?? i understand about things that can affect the compression but lets assume both heads are virgin cast. i know my existing 148 heads are and these 049 head are as cast.

10-13-2012 01:37 AM

cobalt327

Quote:

Originally Posted by OMARS67

do i guess right to think a 119cc head would raise the compression on my 454 BBC. currently i run 148 heads with 122cc but i have pretty tall dome piston. given i use the same gasket for both heads.

First, the advertised volumes are almost never right, the real volume of an unmolested head tends to be a bit more.

That said, the chambers have to be CC'd in order to know exactly what you have. If the heads have been milled, they can be radically different (smaller) than advertised and this can affect the piston to valve clearance. More things to check here. Changing valve sizes, unshrouding or polishing the chamber, valve jobs, etc. can all change the chamber volume.

You are right that a 119cc head will raise the CR over a 122 cc head. But you're only looking at about a 0.2:1 change- so if you're doing this only for the rise in CR, don't bother.

10-12-2012 11:08 PM

OMARS67

hi or low compression??

do i guess right to think a 119cc head would raise the compression on my 454 BBC. currently i run 148 heads with 122cc but i have pretty tall dome piston. given i use the same gasket for both heads.